Synthesis and topological determination of hexakis-substituted 1,4-ditritylbenzene and nonakis-substituted 1,3,5-tritritylbenzene derivatives: Building blocks for higher supramolecular assemblies

FULL PAPER

DOI: 10.1002/ejoc.201201162

Synthesis and Topological Determination of Hexakis-Substituted 1,4-

Ditritylbenzene and Nonakis-Substituted 1,3,5-Tritritylbenzene Derivatives:

Building Blocks for Higher Supramolecular Assemblies

Oliver Plietzsch,^[a]Alexandra Schade,^[a]Andreas Hafner,^[a]Juhani Huuskonen,^[b]

Kari Rissanen,^[b]Martin Nieger,^[c]Thierry Muller,*^[a]and Stefan Bräse*^[a]

Keywords: Supramolecular chemistry / Microporous materials / Nanostructures / Substitution reactions

Based on trityl moieties, novel organic building blocks have

been prepared and structurally investigated. Substituted

hexaphenyl-p-xylene (1,4-ditritylbenzene) as well as ex-

tended analogues thereof were prepared. Furthermore, a

new family based on a 1,3,5-tritritylbenzene motif, connect-

ing three trityl groups through a formal mesitylene unit, was

developed. Both families were further converted through six-

and nine-fold substitution reactions, respectively, to yield po-

tent molecular building blocks for supramolecular assem-

blies.

latter share a broad variety of functional groups, but differ

in the connection pattern (metal coordination, hydrogen-

bonding or covalent bonds). Networks made up entirely of

covalent bonds, may be generated through various reactions

such as click chemistry,^[9a,15–17]cross-coupling,^[11,15,18]or

condensation reactions.^[7]

Introduction

Porous materials play a pivotal role in modern material

chemistry.^[1,2]Over the last decade, hybrid materials with

new properties have been developed with the advent of

metal organic frameworks (MOFs),^[3,4]with hundreds of

new structures exhibiting original properties, in particular

gas-storage abilities.^[5,6]In addition, purely organic, mostly

amorphous materials consisting of supramolecular as-

semblies such as covalent organic frameworks (COFs),^[7]

porous organic polymers (POPs),^[8,9]hyper-cross-linked

polymers (HCPs),^[10]and polymeric porous networks

(PPNs),^[11,12]have emerged. The advantages of these wholly

organic structures are their low densities and their water-

stability. In addition, late-stage functionalization is easily

possible with these materials.^[13]

To create 3-D networks, the “knots” should be non-

planar (sp³type). Therefore, a lot of organic networks are

composed of tetrahedral building blocks. In particular,

symmetrically substituted tetraphenylmethanes (TPMs; 1-

X, Figure 1)^[9,18,19]and related systems (silanes,^[20]ada-

mantanes^[3,21,22]) serve as building blocks of choice. In some

cases, this led to the generation of crystalline structures with

defined pore-size distribution,^[23]although crystallinity is

not a prerequisite to obtain highly porous materials with a

sharp pore-size distribution.^[24]The availability of varying

functional groups on these building blocks is of high inter-

est for screening processes. The combination of building

block shape, functional group, and connection partner as

well as solvents, reaction conditions, and other parameters

influence the structural properties and consequently the ap-

plications of the networks, for example, gas absorption ca-

pacity and selectivity for different gases.

The structures of all these networks are inherently linked

to the shape and connectivity of the building blocks or tec-

tons used.^[14]Mostly rigid organic building blocks bearing

various shapes (linear, triangular and tetrahedral), are being

used, resulting in different 1-, 2-, and 3-D networks. The

[a] Institute of Organic Chemistry and Center for Functional

Nanostructures (CFN), Karlsruhe Institute of Technology

(KIT), Campus South,

In light of these developments, new building block archi-

tectures are highly desirable. In particular, structures bear-

ing octahedral shape would generate unique frameworks.

Some fullerene-based molecules are known to have this

form.^[25]Only a few ditritylbenzenes have been reported so

far.^[26–31]We were among the first to use them as sixfold

connecting tectons.^[32–34]To the best of our knowledge only

two other purely organic structures bearing six anchor

points have been reported so far;^[35]one is a flexible hexaan-

iline^[35a]and the second is based on rigid hexasubstituted

centrohexaindanes.^[35b,35c]

Fritz-Haber-Weg 6, 76131 Karlsruhe, Germany

Fax: +49-721 608 48581

E-mail: thierry.muller@kit.edu

s.braese@kit.edu

Homepage: http://ww w .ioc.kit.edu/braese/english/index.php

[b] Department of Organic Chemistry, Department of Chemistry

P. O. Box 35, 40014 University of Jyväskylä, Finland

[c] Laboratory of Inorganic Chemistry, Department of Chemistry

P. O. Box 55, 00014 University of Helsinki, Finland

Supporting information for this article is available on the

WWW under http://dx.doi.org/10.1002/ejoc.201201162 or from

the author.

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staggered manner when the molecule is observed along the

phenylene axis.

To the best of our knowledge, the only other reported

molecule of this type, in addition to the hexaalcohol 2-

OH,^[26,32]is the unsubstituted 1,4-ditritylbenzene (2-H). Its

synthesis was first described in 1957 by Benkeser and

Schröder in small scale and in poor yield (9%) by reacting

triphenylmethyl radicals with benzene.^[29]Later, they de-

vised a modular and high-yielding synthesis starting from

dilithiobenzene and benzophenone.^[30]Compound 2-H was

used as a reference molecule for their investigations of the

Wieland reaction, involving trityl radicals. No further in-

vestigations, regarding derivatization reactions or structure

modifications were reported. Interestingly, although three

earlier patents exist, there is a general lack of original com-

munications in this area.^[31]

Tritritylarene cores 3-X (nonaphenylmesitylenes; NPMs)

can be seen as three TPM units linked through a shared

phenyl ring (Figure 1). Each of these tectons offer nine an-

chor points for network generation and/or late-stage func-

tionalization. To the best of our knowledge, such molecules

have not yet been reported.

Herein, we report some new organic tectons exhibiting

pseudo-octahedral structure (2-X; Figure 1) and novel ex-

panded analogues thereof. In addition, we report synthetic

access to the unprecedented 1,3,5-tritylbenzene (3-H) and

its ninefold functionalization.

Figure 1. Tectons 1–3-X based on a trityl substructure; X-ray struc-

ture of a HPX derivative 2-OH.^[32]

Results and Discussion

We optimized the published synthesis of 1,4-ditritylbenz-

As a part of an ongoing nanostructure project, we are ene (2-H) by performing the first step by reacting inexpen-

interested in easily accessible organic core structures^[22,36]sive and commercially available dimethyl terephthalate (4)

and, among others, in the generation of three-dimensional with phenyllithium in 88% yield (Scheme 1). In the original

networks built up from organic DNA hybrid building publication, p-bis(diphenylhydroxymethyl)benzene (5-H)

blocks connected by Watson–Crick base pairing.^[37,38]In was obtained in only 25% yield.^[30]The second step, the

this context, tetrakis(4-hydroxyphenyl)methane (1-OH) was addition of 5-H^[39]to aniline in a Friedel–Crafts alkylation

used as a tetrahedral three-dimensional scaffold, the hy- type reaction and subsequent removal of the amine group

droxyl groups of which can be used to attach the DNA through diazotization and addition of a hydride donor, was

strands which act as sticky sites. Based on the first encour- carried out as described by Benkeser and Schröder

aging results obtained with this system,^[37]expanded struc- (Scheme 1).^[29,30]

tures having a rigid three-dimensional motif and bearing

Thus, 1,4-ditritylbenzene (2-H) was readily available on

additional hydroxyl groups, became of interest.^[32]Thus, a multigram scale in a good overall yield of 65%. With this

hexaphenyl-p-xylene (HPX) cores (2-X), namely 1,4-bis- HPX core in hand, we started investigating direct sixfold

[tris(4Ј-hydroxyphenyl)methyl]benzene (2-OH), first synthe- para-substitutions, in analogy to reactions performed on the

sized by Hatano and Kato in 2008,^[26]came into focus. This TPM core.^[16a,37]We explored five reactions, which deliv-

molecule can be regarded as two TPM units linked through ered interesting key compounds for further derivatization

a shared phenyl ring (Figure 1).

reactions. The reaction conditions for these sixfold substitu-

Using an optimized synthetic procedure, we were able to tion reactions have to be chosen very carefully. On the one

obtain the pure material on a gram scale. We compared the hand, the reaction has to go to completion to obtain the

ability to generate DNA-based networks of tectons 2-OH sixfold substituted derivative and to avoid less substituted

and tetrakis(4-hydroxyphenyl)methane (1-OH).^[32]The ma- species, which are very difficult to separate by classical puri-

terial generated by the expanded HPX building block fication methods. On the other hand, applying very harsh

showed different and promising properties compared with conditions can lead to the formation of byproducts such as

the TPM core. An X-ray analysis of tecton 2-OH revealed meta- and poly-substituted derivatives. The results obtained

a pseudo-octahedral structure in the solid state.^[32]Indeed, under the optimized reaction conditions for these sixfold

three phenyl rings of the trityl moieties are oriented in a para-substitution reactions are summarized in Table 1.

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1,4-Ditrityl- and 1,3,5-Tritritylbenzene Derivatives

Scheme 1. Optimized synthesis of unsubstituted 1,4-ditritylbenzene (2-H) in 65% overall yield.

Table 1. Sixfold substitutions starting from 1,4-ditritylbenzene (2- ance with our investigations on the TPM cores. Ac-TPM

H).

was the only compound in the TPM series for which traces

of meta-substituted byproducts could be detected.^[42]

Single crystals of hexabromide 2-Br and hexaiodide 2-I

were obtained and X-ray diffraction molecular structures of

these HPXs were measured (Figure 2).^[43]Both molecules

showed the expected 3-D structure in the solid state, which

Entry HPX

Reaction conditions

Yield [%]

1

2

3

4

5

2-Br

2-I

Br₂, room temp., 1 h

92

55

46

21

40

I₂, PIFA,^[a]CCl₄, 60 °C, 6 d

2-SO₃H ClSO₃H, CH₂Cl₂, 35 °C, 90 min.

2-NO₂

HNO₃, glacial acetic acid, 70 °C, 18 h

AcCl, AlCl₃, CS₂, 75 °C, 18 h

2-Ac^[b]

[a] Phenyliodine bis(trifluoroacetate). [b] Ac = COCH₃.

Hexabromide 2-Br was obtained in pure form and excel-

lent yield (92%) after simple recrystallization (Table 1, en-

try 1), as was hexaiodide 2-I, albeit in only moderate 55%

yield, mostly due to poor solubility in common organic sol-

vents (Table 1, entry 2). This poor solubility was also ob-

served for the hexasulfonic acid derivative 2-SO₃H, which

was obtained in pure form and 46% yield after simple

washing of the crude reaction mixture (Table 1, entry 3).^[40]

The synthesis of the hexanitro derivative 2-NO₂^[41]is a good

example showing the importance of the reaction conditions

(Table 1, entry 4). When a mixture of HNO₃(1 mL) in gla-

cial acetic acid (15 mL) was used, the hexanitro compound

was obtained in 21% yield after column chromatography.

Performing the reaction in a different ratio of nitric and

acetic acid led to byproducts that could not be separated

from the desired HPX derivative 2-NO₂by standard purifi-

cation methods. For the hexaacetyl derivative 2-Ac, which

could be obtained in 40% yield, meta-substituted phenyl

rings were always formed irrespective of the reaction condi-

Figure 2. Molecular structure of hexabromide 2-Br and hexaiodide

tions used (Table 1, entry 5). This observation is in accord- 2-I shown along the phenylene axis.

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we previously reported for hexaalcohol 2-OH. The three ride, yielding hexaalkyne 2-CCH in 65% yield over two

phenyl rings of the two trityl moieties are arranged in a steps (Scheme 2).

staggered manner, leading to a pseudo-octahedral shape.

Hexaalkyne derivative 2-CCH is expected to be a very

With these HPXs in hand, we investigated further important compound for modular syntheses such as cross-

derivatization reactions. Transformation of 2-NO₂into the coupling reactions, click,^[44]or thiol-yne^[45]reactions.

corresponding hexamine was unsuccessful, and no conver-

Furthermore, we could successfully perform a sixfold li-

sion was observed when hexanitro derivative 2-NO₂was thiation^[46]of hexabromide 2-Br using n-butyllithium. The

treated with hydrogen gas at atmospheric pressure and hexalithiated intermediate was treated with methyl iodide

12 bar, respectively, in the presence of palladium on char- as electrophile, yielding 1,4-bis[tris(4Ј-methylphenyl)meth-

coal (Pd/C), even under elevated temperatures (results not yl]benzene (2-Me) in moderate yield after purification by

shown). 2-Br and 2-I served as starting materials for ad- column chromatography (Scheme 3). The sixfold lithiation

ditional sixfold reactions. First, the well-established Sono- and subsequent reaction with an electrophile using readily

gashira reaction was performed; in this palladium-catalyzed available hexabromide 2-Br should give access to a broad

cross-coupling reaction, hexaiodide 2-I was treated with tri- variety of products.

methylsilylacetylene and the sixfold cross-coupling product

After these encouraging results with hexabromide 2-Br,

was directly deprotected with tetrabutylammonium fluo- we investigated the scope of the bromination reaction using

Scheme 2. Synthesis of 1,4-bis[tris(4Ј-ethynylphenyl)methyl]benzene (2-CCH) through sixfold Sonogashira cross-coupling reaction.

Scheme 3. Sixfold lithiation of hexabromide 2-Br and reaction with methyl iodide as electrophile.

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1,4-Ditrityl- and 1,3,5-Tritritylbenzene Derivatives

Scheme 4. Selective bromination of dianiline compound 6.

dianiline compound 6. The latter was selectively brominated protected species 2-OTf in 24% yield, showing that all hy-

in elementary bromine at room temperature within 20 min droxyl groups are reactive in principle but giving low yields

(Scheme 4). Pure compound 7 was obtained in 96% yield even for this simple reaction (Scheme 5). The low yield

after simply washing the residue.

might be attributed to the solubility of hexaalcohol 2-OH,

In addition to these reactions, hexaalcohol 2-OH, pre- which is generally very low both in organic solvents and in

pared according the procedure depicted in Scheme 5 and aqueous media. Although obtained in only poor yield, 2-

published earlier,^[32]could be converted into its triflate-pro- OTf is nevertheless a very interesting compound for further

tected form. Reaction with triflic anhydride led to the fully derivatization reactions. The molecular structure of 5-OMe,

Scheme 5. Synthesis of 1,4-bis[tris(4Ј-hydroxyphenyl)methyl]benzene (2-OH) and subsequent sixfold triflate formation.

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an intermediate in the synthesis of hexaalcohol and -triflate, avoid sixfold reactions, we chose to use the second pathway

was determined and shows once more the pseudo-octahe- to lengthen the two trityl moieties. As shown before, most

dral shape of this class of compounds (Figure 3).

sixfold reactions on 1,4-ditritylbenzene derivatives (2-X) are

challenging and sometimes low yielding. We feared that

these difficulties would become worse with an increasing

sized scaffold, mainly because its solubility decreases with

increasing size.

Building block C (11-H) is readily available in a few steps

from substituted benzophenones 12-X (see the Supporting

Information for details). Subsequent Sonogashira coupling

provided carbinol 16 in good overall yield (Scheme 7).

Alkyne 17-CCH (X = CCH), which was required for di-

merization, was accessible from 16 through a sequence of

Friedel–Crafts alkylation, triflate formation, cross-coupling

with trimethylsilylethyne, and desilylation (Scheme 8).

Reaction of alkyne 17-CCH with 1,4-diiodobenzene un-

der palladium catalysis (Sonogashira conditions) provided

the HPXXL core 9-OMe in 37% (69% based on recovered

starting material; Scheme 9, left). This core exhibits a three-

dimensional calculated latitude of 3.6 nm.

Figure 3. Molecular structure of compound 5-OMe, which is a pre-

cursor of hexaalcohol 2-OH.

Because it was necessary to convert the triflate protected

We next turned to an expanded series of the HPX core, phenol 17-OH (X = OH) into alkyne 17-CCH and connect

which was synthesized using phenylacetylene spacers. The two of these building blocks through cross-coupling with

so-called HPXXL system was designed to have additional 1,4-diiodobenzene, we also investigated a shorter route. An

spacers formally enlarging every C–aryl bond by a phenyl- easier alternative would be the cross-coupling reaction of

acetylene unit when compared to the HPX skeleton. This triflate intermediate 17-OTf (X = OTf) with 1,4-diethyn-

enlargement is thought to reduce the steric hindrance at the ylbenzene, leading to HPXXL 9-OMe with less synthetic

trityl moieties, leaving more space for the attachment of effort (Scheme 9, right). Unfortunately, the use of 1,4-dieth-

larger sticky sites. Two main advantages are expected to ynylbenzene turned out to be inappropriate for this reac-

arise from this enlargement. Firstly, generally higher surface tion. The triflate-protected starting material 17-OTf could

area and larger pore-size are anticipated. Secondly, the indeed be completely recovered after the reaction, whereas

acetylene moieties are often used to prepare inherently con- 1,4-ethynylbenzene had almost totally disappeared. Similar

ducting or semiconducting materials and these units should problems regarding the reactivity of 1,4-ethynylbenzene

allow further functionalization with, for example, organo- were observed for the generation of HCPs through click

metallic complexes.^[47]This could, in turn, lead to the gener- chemistry.^[16a,42]In addition, reaction of the test building

ation of new microporous heterogeneous catalysts. Retro- block 18 with 1,4-ethynylbenzene delivered product 19 in

synthetically, the HPXXL core A is built from a carbinol only poor yield (13%; Scheme 10). Neither longer reaction

derivative B, which, in turn, is derived from the trityl deriva- times nor the use of more equivalents of 18 resulted in bet-

tive C (11-H; Scheme 6).

ter yields.

In principle, two synthetic approaches were envisaged to

We then tried to generate the hexaalcohol from the ex-

generate the HPXXL core 9-OR. One route starts from the panded core 9-OMe. The desired deprotection of the meth-

central unit, elongating both trityl moieties in parallel. The oxy groups failed using boron tribromide. The cleavage was

second option is to build up the tetraphenylmethane build- thus explored on the test compound (4-methoxyphenyl)-

ing block B and connect two of them through a symmetri- phenylacetylene. We observed that the deprotection is kinet-

cal 1,4-substituted bifunctional phenylene (Scheme 6). To ically favored at low temperatures (–20 to 0 °C) and using

Scheme 6. Retrosynthetic synthesis of the expanded HPXXL system 9-OR.

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1,4-Ditrityl- and 1,3,5-Tritritylbenzene Derivatives

Scheme 7. Synthesis of carbinol derivative 16.

when used to deprotect 9-OMe (results not shown). We are

currently exploring other possibilities to effectively generate

the HPXXL hexaalcohol starting from 9-OMe.

After preparing the HPX and expanded HPXXL cores,

we wanted to explore the scope of our methodology and

investigated 1,3,5-tritritylarene and nonaphenyl mesitylene

cores, namely tritritylbenzene derivatives (3-X; Fig-

ure 1).^[48,49]In these types of molecules, the central phenyl

ring is crowded by three sterically demanding trityl moie-

ties. Some related compounds such as hexaaryltruxene or

analogues in which the central arene moiety is part of three

fluorene units,^[50]have shown interesting properties in mate-

rial chemistry.^[51,52]

In a first step, we investigated the synthesis of unsubsti-

tuted NPM 3-H. In analogy to the synthesis of HPX

2-H, we used commercially available trimethyl benzene-

1,3,5-tricarboxylate (20) as starting material (Scheme 11).

The sixfold addition of phenyllithium to the three ester moi-

eties delivered the intermediate triol 21-H in a remarkable

91% yield. It was found that when treating triol 21-H with

Scheme 8. Synthesis of alkyne 17-CCH (X = CCH).

stoichiometric amounts of boron tribromide. These condi- aniline in a Friedel–Crafts type reaction at elevated tem-

tions allowed addition to the triple bond to be suppressed perature in glacial acetic acid, addition of HCl was essential

when applied to the test system but, unfortunately, failed to obtain high yields. Triamine 22-NH₂was obtained in

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Scheme 9. Synthesis of the HPXXL 9-OCH₃.

Scheme 10. Synthesis of semi-expanded 1,4-ditritylbenzene derivative 19.

pure form without column chromatography by a simple

In analogy to the Friedel–Crafts reaction of 21-H with

washing procedure. Desamination of 22-NH₂through di- aniline, 21-H was treated with phenol to give triol 22-OH,

azotization delivered the desired 1,3,5-tritritylbenzene 3-H, in moderate yields (Scheme 12). Product 22-OH was ac-

which could again be isolated in excellent yield and in pure companied by the formation of side products and required

form by simple filtration followed by washing. NPM 3-H, purification by column chromatography over silica gel.

obtained in 77% overall yield by a three step procedure in

The molecular structure of 21-H is shown in Figure 4.

gram scale, is similar to the related compounds TPM 1-H As expected for trityl-based cores, the phenyl rings lie above

and HPX 2-H, and is a high-melting hydrocarbon (melting and below the plane of the central benzene ring, the hy-

point with decomposition above 280 °C).

droxyl groups, however, are in-plane.

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1,4-Ditrityl- and 1,3,5-Tritritylbenzene Derivatives

Scheme 11. Synthesis of unsubstituted 1,3,5-tritritylbenzene (3-H).

sumed. The crude mixture was demethylated at low tem-

perature to furnish nonaphenol 3-OH in moderate yield

over two steps. Finally, nonatriflate 3-OTf was obtained in

good yield by treatment with triflic anhydride.

Scheme 12. Synthesis of trihydroxy-1,3,5-tritritylbenzene (22-OH).

Figure 4. Molecular structure of 21-H.

Likewise, the nonamethoxy derivative 21-OMe was pre-

pared from triester 20 and 4-lithioanisole, generated from

bromoanisole, in 70% yield (Scheme 13). The yield was

comparable (63%) when the reaction was carried out with

the corresponding Grignard reagent (results not shown). As

for 21-H, the subsequent Friedel–Crafts product was

Scheme 13. Synthesis of functionalized tritritylbenzene derivatives.

Single crystals of 3-OTf could be obtained by recrystalli-

formed along with side products. To minimize their forma- zation of the purified compound from tetrahydrofuran

tion, the progress of the reaction was monitored by TLC (THF). The molecular structure of 3-OTf is shown in Fig-

and stopped as soon as 21-OMe had been completely con- ure 5.

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An optimized synthesis of HPX 2-H was presented and

further functionalized through sixfold substitution reac-

tions to generate a series of interesting core structures.

Hexaalcohol 2-OH, as well as hexahalides 2-Br and 2-I,

were transformed into hexatriflate 2-OTf, the hexalithio de-

rivative, and engaged in a Sonogashira cross-coupling reac-

tion, respectively. This led to new interesting structures and

showed the broad applicability of most of the precursor

cores. In the HPX series, we have furthermore presented the

synthesis of an expanded core named HPXXL. Finally, we

have adapted our synthetic approach to the synthesis of

completely novel NPM cores 3-X, bearing nine functionali-

zation or connection sites. We have shown that functionali-

zation is possible with these cores in moderate to good

yields.

Figure 5. Molecular structure of 3-OTf.

Because the majority of the presented structures are eas-

ily accessible in a few steps in gram scale, these rigid cores

should readily find application in material chemistry. We

are currently investigating the potential of some of these

compounds to act as tectons in purely organic networks.

We then investigated the ninefold substitution reaction of

the NPM core 3-H. The temperature, stoichiometry, di-

lution, and reaction times were optimized to minimize side

product formation, which mainly consisted of meta-substi-

tuted products (Table 2). The functionalization of parent

hydrocarbon 3-H to nonabromide 3-Br (Table 2, entry 1) or

nonaiodide 3-I (Table 2, entry 2) proceeded smoothly. As

observed for the HPX core before (Table 1), bromination

gave better yields than iodination. The nonanitro com-

pound 3-NO₂(Table 2, entry 3) and the nonasulfonic acid

3-SO₃H (Table 2, entry 4) were synthesized in good and

moderate yields, respectively. These ninefold reactions prove

that the NPM core can indeed be functionalized and thus

should find application in material chemistry.

Experimental Section

1

General Remarks: H NMR spectra were recorded with a Bruker

AM 400 (400 MHz) or a Bruker Avance DRX (500 MHz) spec-

trometer as solutions in CDCl₃or [D₆]DMSO. Chemical shifts are

expressed in parts per million (ppm, δ) downfield from tetramethyl-

silane (TMS; δ = 0 ppm) and are referenced to CHCl₃(δ =

7.26 ppm) or DMSO (δ = 2.50 ppm) as internal standard. All cou-

pling constants are absolute values and J values are expressed in

Hertz [Hz]. The description of signals include: s singlet, br. s broad

singlet, d doublet, m multiplet, dd doublet of doublets, AAЈBBЈ

spin system of hydrogen atoms on a para-substituted phenyl ring.

The spectra were analyzed according to first order. ¹³C NMR spec-

tra were recorded with a Bruker AM 400 (100 MHz) or a Bruker

Avance DRX (125 MHz) spectrometer as solutions in CDCl₃or

[D₆]DMSO. Chemical shifts are expressed in parts per million

(ppm, δ) downfield from tetramethylsilane (TMS; δ = 0 ppm) and

are referenced to CHCl₃(δ = 77.4 ppm) or DMSO (δ = 39.5 ppm)

as internal standard. The signal structure was analyzed by DEPT

and is described as follows: + denotes a primary or tertiary C-atom

(positive signal), – a secondary C-atom (negative signal), and q a

quaternary C-atom (no signal). Mass spectra (FAB and EI-MS)

were recorded with a Finnigan MAT 95 spectrometer under fast

atom bombardment (FAB) conditions with nitrobenzyl alcohol as

matrix and reference. The molecular fragments are quoted as the

relation between mass and charge (m/z), the intensities as a percen-

tage relative to the intensity of the base signal (100%). The quasi-

molecular ion is abbreviated [M + H⁺] for FAB-MS. IR spectra

were recorded with a FTIR Bruker IFS 88 spectrometer. IR spectra

were recorded using the attenuated total reflection technique

(ATR) or the DRIFT technique (diffused reflectance infrared Fou-

rier transform-spectroscopy) for solids. IR spectra of oils were de-

termined as KBr plates. The absorption band positions are given

Table 2. Synthesis of functionalized tritritylbenzene derivatives.

Entry

NPM Reaction conditions

Yield [%]

1

2

3

4

3-Br

3-I

Br₂, room temp., 1 h

I₂, PIFA, CCl₄, 80 °C, 24 h

83

28

60

38

3-NO₂HNO₃, –5 °C – room temp., 12 h

3- ClSO₃H, CH₂Cl₂, room temp. –

SO₃H 35 °C, 12 h

in wave numbers ν in cm^–1. Analytical thin-layer chromatography

Conclusions

˜

(TLC) was carried out on Merck silica gel coated aluminum plates

(silica gel 60, F₂₅₄), detected under UV-light at 254 nm. Solvent

mixtures are given as volume/volume. Melting points (m.p.) were

determined with a Julabo ED-5 fully automated melting point ap-

paratus and are uncorrected. All values are given as single points

We have synthesized new trityl-substituted arenes and ex-

plored their potential for further functionalization in order

to act as molecular building blocks in supramolecular as-

semblies.

292

www.eurjoc.org

Eur. J. Org. Chem. 2013, 283–299

1,4-Ditrityl- and 1,3,5-Tritritylbenzene Derivatives

measured by the apparatus according to the starting point of de-

composition.

3-OTf: Yellow crystals; C₇₂H₃₉F₂₇O₂₇S₉+C₆H₆; M = 2215.68; crys-

tal size 0.40ϫ0.25ϫ0.20 mm; monoclinic; space group C2/c (No.

15); a = 28.845(3) Å, b = 17.401(2) Å, c = 35.200(4) Å, β =

93.06(1)°; V = 17704(3) Å³; Z = 8; ρ(calcd.) = 1.663 Mgm^–3; F(000)

= 8928; μ = 0.361 mm^–1; 59036 reflections (2θ_max= 55°), 19963

unique [R_int= 0.029], 1232 parameters, 411 restraints, R₁[IϾ2σ(I)]

= 0.102, wR₂(all data) = 0.287, GooF = 1.03, largest diff. peak

and hole 2.175 and –1.785 eÅ^–3. The porosity was 9.5%^[54]and the

packing index 62.5.^[54]

Solvents, reagents and chemicals were purchased from Acros,

ABCR, Alfa Aesar, Fluka, Merck, Riedel-de Haën, or Sigma-Ald-

rich. Ethyl acetate, cyclohexane and dichloromethane were distilled

from calcium hydride prior to use. Anhydrous toluene and THF

were distilled from sodium using benzophenone as indicator in the

case of THF. All other solvents, reagents, and chemicals were used

as purchased. All reactions involving moisture-sensitive reactants

were executed under an argon atmosphere, using oven-dried and/

or flame-dried glassware.

5-OMe: Colorless crystals; C₃₆H₃₄O₆+C₆H₁₂; M = 646.79; crystal

size 0.50ϫ0.45ϫ0.40 mm; monoclinic; space group P2₁/n (No.

14); a = 19.461(1) Å, b = 8.079(1) Å, c = 22.152(1) Å, β =

106.20(1)°; V = 3344.6(5) Å³; Z = 4; ρ(calcd.) = 1.284 Mgm^–3;

F(000) = 1384; μ = 0.085 mm^–1; 43834 reflections (2θ_max= 55°),

7647 unique [R_int= 0.022], 443 parameters, 2 restraints, R₁

[IϾ2σ(I)] = 0.040, wR₂(all data) = 0.102, GooF = 1.06, largest

diff. peak and hole 0.323 and –0.211 eÅ^–3. The porosity was

18.1%^[54]and the packing index 59.5.^[54]

Crystal Structure Studies: Single-crystal X-ray diffraction studies

were carried out with a Bruker-Nonius Kappa-CCD diffractometer

at 123(2) K using Mo-K_αradiation (λ = 0.71073 Å). Direct Meth-

ods (SHELXS-97^[53]) were used for structure solution, and full-ma-

trix least-squares refinement on F²(SHELXL-98^[53]). H atoms were

localized by difference Fourier synthesis and refined using a riding

model [H(O) free]. Semi-empirical absorption corrections were ap-

plied for 2-Br-thf, 2-Br-dmf, 2-I, and 3-OTf. For 21-H an extinction

correction was applied.

21-H: Pale-yellow crystals; C₄₅H₃₆O₃; M = 624.74; crystal size

0.48ϫ0.16ϫ0.08 mm; monoclinic; space group P2₁/c (No. 14); a

=

9.1147(9) Å, b = 23.1895(15) Å, c = 15.7992(13) Å, β =

In 2-Br-thf, 2-Br-dmf, and 2-I there was either a slight disorder of

the halogen atoms between the p- and the m-position in the range

98:2 or a 2nd substitution in the m-position (approx. 2%), which

could not be refined reasonably. In 3-OTf, two of the nine 4-tri-

fluoromethylsulfonylphenyl substituents were disordered.

90.850(8)°; V = 3339.0(5) Å³; Z = 4; ρ(calcd.) = 1.243 Mgm^–3;

F(000) = 1320; μ = 0.076 mm^–1; 21346 reflections (2θ_max= 50°),

5879 unique [R_int= 0.035], 443 parameters, 6 restraints, R₁

[IϾ2σ(I)] = 0.040, wR₂(all data) = 0.089, GooF = 1.05, largest

diff. peak and hole 0.197 and –0.164 eÅ^–3. The porosity was

0.9%^[54]and the packing index 67.0.^[55]

2-Br-thf: Yellow crystals; C₄₄H₂₈Br₆+C₄H₈O; M = 1108.23; crystal

size 0.30ϫ0.30ϫ0.10 mm; monoclinic; space group C2/c (No. 15);

a = 13.903(1) Å, b = 14.470(1) Å, c = 21.365(2) Å, β = 107.19(1)°;

V = 4106.1(6) Å³; Z = 4; ρ(calcd.) = 1.793 Mgm^–3; F(000) = 2168;

μ = 5.904 mm^–1; 21155 reflections (2θ_max= 50°), 3610 unique [R_int

= 0.052], 271 parameters, 66 restraints, R₁[IϾ2σ(I)] = 0.054, wR₂

(all data) = 0.143, GooF = 1.09, largest diff. peak and hole 1.877

and –0.862 eÅ^–3. The porosity was 12.9%^[54]and the packing index

61.7.^[55]

CCDC-855064 (for 2-Br-thf), -855065 (for 2-Br-dmf), -855066 (for

2-I), -785245 (for 2-OH), -855067 (for 3-OTf), -855068 (for 5-OMe),

and -855069 (for 21-H) contain the supplementary crystallographic

data for this paper. These data can be obtained free of charge from

The Cambridge Crystallographic Data Centre via www.ccdc.cam.

ac.uk/data_request/cif.

Syntheses of 1,4-Ditritylbenzene Derivatives

2-Br-dmf: Colorless crystals; C₄₄H₂₈Br₆+C₃H₇NO; M = 1109.22;

crystal size 0.20ϫ0.15ϫ0.10 mm; monoclinic; space group C2/c

(No. 15); a = 13.813(1) Å, b = 14.511(1) Å, c = 21.449(2) Å, β =

106.12(1)°; V = 4130.2(6) Å³; Z = 4; ρ(calcd.) = 1.784 Mgm^–3;

F(000) = 2168; μ = 5.870 mm^–1; 23724 reflections (2θ_max= 50°),

3622 unique [R_int= 0.034], 248 parameters, 10 restraints, R₁

[IϾ2σ(I)] = 0.052, wR₂(all data) = 0.149, GooF = 1.04, largest

diff. peak and hole 2.393 and –0.530 eÅ^–3. The porosity was

12.5%^[54]and the packing index 61.4.^[55]

1,4-Ditritylbenzene (2-H): Dianiline 6 was suspended in glacial

acetic acid (600 mL) and hypophosphoric acid (70 mL, 50% aque-

ous solution). At 10 °C, NaNO₂(2.34 g, 33.9 mmol, 3 equiv.) was

added in small amounts under vigorous stirring. The reaction mix-

ture was stirred overnight at room temperature, then water

(100 mL) was added and the formed solid was filtered off, washed

with water, methanol, and diethyl ether (75 mL each) and dried in

vacuo. Without further purification, 1,4-ditritylbenzene (2-H;

4.70 g, 96% and 74% overall yield) was obtained as a beige powder;

1

R_f= 0.30 (cyclohexane/ethyl acetate, 25:1); m.p. 296 °C (dec.). H

2-I: Colorless crystals; C₄₄H₂₈I₆+C₄H₈O; M = 1390.17; crystal size

0.25ϫ0.20ϫ0.15 mm; monoclinic; space group C2/c (No. 15); a =

14.276(1) Å, b = 14.866(1) Å, c = 21.729(2) Å, β = 106.68(1)°; V =

4417.4(6) Å³; Z = 4; ρ(calcd.) = 2.090 Mgm^–3; F(000) = 2600; μ =

NMR (400 MHz, CDCl₃): δ = 7.11 (s, 4 H, 2-H, 3-H), 7.21–7.31

(m, 30 H, 2Ј-H, 3Ј-H, 4Ј-H) ppm. ¹³C NMR (100 MHz, CDCl₃): δ

= 64.6 [C_q, C(Ar)₄], 125.9 (+, C-4Ј), 127.3 (+, C-3Ј), 130.3 (+, C-

2, C-3), 131.2 (+, C-2Ј), 144.2 (C_q, C-1, C-4), 146.7 (C_q, C-1Ј) ppm.

4.255 mm^–1; 18371 reflections (2θ_max= 55°), 5067 unique [R_int

=

IR (DRIFT): ν = 3056, 3030, 1956, 1815, 1701, 1596, 1491, 1443,

˜

0.041], 246 parameters, 16 restraints, R₁[IϾ2σ(I)] = 0.066, wR₂

(all data) = 0.176, GooF = 1.07, largest diff. peak and hole 3.507

and –1.006 eÅ^–3. The porosity was 13.1%^[54]and the packing index

60.7.^[55]

1405, 1370, 1319, 1186, 1083, 1035, 1002, 890, 824, 748, 702, 642,

632, 532 cm^–1. MS (70 eV, EI): m/z (%) = 562 (76) [M⁺], 485 (100)

[M⁺– C₆H₅], 409 (24) [C₃₂H₂₅⁺], 319 (33) [C₂₅H₁₉⁺], 243 (59)

[C₁₉H₁₅⁺], 165 (60) [C₁₃H₉⁺]. HRMS (EI): calcd. for C₄₄H₃₄

562.2660; found 562.2659.

2-OH:^[32]Pale-yellow crystals; C₄₄H₃₄O₆+5 ϫ C₆H₆; M = 1049.25;

¯

crystal size 0.50ϫ0.25ϫ0.20 mm; triclinic; space group P1 (No.

2); a = 10.729(1) Å, b = 11.136(1) Å, c = 13.397(1) Å, α = 75.80(1)°,

1,4-Bis[tris(4Ј-bromophenyl)methyl]benzene (2-Br): Compound 2-H

(3.00 g, 5.33 mmol, 1 equiv.) was added in small portions to pure

β = 74.97(1)°, γ = 78.62(1)°; V = 1483.3(2) Å³; Z = 1; ρ(calcd.) =

1.175 Mgm^–3; F(000) = 556; μ = 0.073 mm^–1, 21803 reflections bromine (without any solvent) (4.9 mL, 15.3 g, 96.0 mmol,

(2θ_max= 55°), 6735 unique [R_int= 0.035], 370 parameters, 3 re-

straints, R₁[IϾ2σ(I)] = 0.051, wR₂(all data) = 0.124, GooF =

1.02, largest diff. peak and hole 0.247 and –0.295 eÅ^–3. The poros-

ity was 53.1%^[54]and the packing index 37.9.^[54]

18 equiv.) under vigorous stirring. The reaction mixture was stirred

for 1 h at room temperature and then cooled to –78 °C. Ethanol

(50 mL) was added and the reaction mixture was warmed to room

temperature. The solid was filtered off and washed with satd. aque-

Eur. J. Org. Chem. 2013, 283–299

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293

T. Muller, S. Bräse et al.

FULL PAPER

ous Na₂S₂O₃solution (100 mL) and water (250 mL). Drying in

vacuo afforded 2-Br (5.15 g, 92%) as a light-yellow solid; R_f= 0.72

(cyclohexane/ethyl acetate, 10:1); m.p. 323 °C (dec.). ¹H NMR

(400 MHz, CDCl₃): δ = 6.99 (AAЈBBЈ, J = 8.7 Hz, 12 H, 2Ј-H),

7.01 (s, 4 H, 2-H, 3-H), 7.38 (AAЈBBЈ, J = 8.7 Hz, 12 H, 3Ј-

H) ppm. ¹³C NMR (100 MHz, CDCl₃): δ = 63.6 [C_q, C(Ar)₄], 120.7

(C_q, C-4Ј), 130.2 (+, C-2, C-3), 130.9 (+, C-2Ј), 132.5 (+, C-3Ј),

1,4-Bis[tris(4Ј-acetylphenyl)methyl]benzene (2-Ac): A mixture of 2-

H (0.25 g, 0.44 mmol, 1 equiv.), acetyl chloride (0.24 mL, 0.268 g,

3.42 mmol, 7.7 equiv.) and anhydrous aluminum trichloride (0.42 g,

0.45 mmol, 7.6 equiv.) in CS₂(10 mL) was heated to reflux for 18 h.

After cooling to room temperature, the solvent was decanted. Ice

(10 g), concd. HCl (7 mL), and CH₂Cl₂(30 mL) were added to the

residue and the mixture was stirred until the precipitate had com-

143.6 (C , C-1, C-4), 144.6 (C , C-1Ј) ppm. IR (DRIFT): ν = 3545, pletely dissolved. The organic layer was separated, dried with

˜

q

3365, 3054, 2929, 2834, 2740, 2599, 2355, 1940, 1700, 1601, 1575,

MgSO₄and concentrated under reduced pressure. Flash column

1504, 1419, 1390, 1312, 1215, 1173, 1115, 1015, 918, 809, 717, 666, chromatography (cyclohexane/ethyl acetate, 3:1Ǟ1:1) afforded the

628, 543, 445, 417 cm^–1.

product 2-Ac (143 mg, 40%) as a yellow solid; R_f= 0.22 (cyclohex-

ane/ethyl acetate, 1:1); m.p. 134 °C (dec.). ¹H NMR (400 MHz,

CDCl₃): δ = 2.58 (s, 18 H, CH₃), 7.10 (s, 4 H, 2-H, 3-H), 7.29

(AAЈBBЈ, J = 8.5 Hz, 12 H, 3Ј-H), 7.87 (AAЈBBЈ, J = 8.5 Hz, 12

H, 2Ј-H) ppm. ¹³C NMR (100 MHz, CDCl₃): δ = 26.6 (+, CH₃),

65.0 [C_q, C(Ar)₄], 127.9 (+, C-2Ј), 130.4 (+, C-2, C-3), 130.9 (+, C-

3Ј), 135.3 (C_q, C-4Ј), 143.4 (C_q, C-1, C-4), 150.4 (C_q, C-1Ј), 197.6

1,4-Bis[tris(4Ј-iodophenyl)methyl]benzene (2-I): Compound 2-H

(3.00 g, 5.33 mmol, 1 equiv.), iodine (7.98 g, 31.4 mmol, 5.9 equiv.)

and [bis(trifluoroacetoxy)iodo]benzene (18.1 g, 42.1 mmol,

7.9 equiv.) were suspended in carbon tetrachloride (60 mL) and

stirred for 6 d at 60 °C under an argon atmosphere. The solvent was

removed under reduced pressure and the residue was suspended in

acetone (150 mL) and stirred for 2 h at room temperature. The so-

lid was filtered off and washed with acetone (50 mL). Drying in

vacuo afforded the product 2-I (3.90 g, 55%) as a white powder; R_f

= 0.61 (cyclohexane/ethyl acetate, 25:1); m.p. 377 °C (dec.). ¹H

NMR (300 MHz, CDCl₃): δ = 6.85 (AAЈBBЈ, J = 8.5 Hz, 12 H,

2Ј-H), 6.99 (s, 4 H, 2-H, 3-H), 7.57 (AAЈBBЈ, J = 8.5 Hz, 12 H, 3Ј-

H) ppm. ¹³C NMR (100 MHz, [D₆]DMSO): δ = 63.3 [C_q, C(Ar)₄],

92.8 (C_q, C-4Ј), 129.5 (+, C-2, C-3), 132.4 (+, C-2Ј), 136.6 (+, C-

(C , CO) ppm. IR (DRIFT): ν = 2926, 1682, 1600, 1500, 1407,

˜

q

1356, 1266, 1190, 1069, 1015, 959, 820, 761, 716, 691, 665, 591,

564, 525, 420 cm^–1. MS (FAB, 3-NBA): m/z (%) = 815 (5) [M +

H⁺], 154 (100). HRMS (FAB): calcd. for C₅₆H₄₇O₆815.3373; found

815.3373.

1,4-Bis[tris(4Ј-ethynylphenyl)methyl]benzene (2-CCH): A mixture of

2-I (100 mg, 81.0 μmol, 1 equiv.), [PdCl₂(PPh₃)₂] (12.8 mg,

18.2 μmol, 0.2 equiv.), CuI (6.90 mg, 3.62 μmol, 0.5 equiv.) and tri-

methylsilylacetylene (90 μL, 67.0 mg, 0.68 mmol, 9 equiv.) in anhy-

drous THF (3 mL) and anhydrous triethylamine (5 mL) was stirred

for 16 h at 75 °C under an argon atmosphere. The solvents were

removed under reduced pressure and the residue was taken up in

1 m HCl (25 mL) and CH₂Cl₂(50 mL), the organic phase was sepa-

rated and the aqueous phase was extracted with CH₂Cl₂

(3ϫ50 mL). The combined organic layers were dried with MgSO₄

and the solvent was removed under reduced pressure. The crude

trimethylsilyl-protected acetylene 2-CCTMS was used in the next

step without further purification. A solution of the crude trimethyl-

silyl-protected acetylene 2-CCTMS in benzene (7 mL) and acetoni-

trile (7 mL) was treated with tetrabutylammonium fluoride (0.13 g,

0.49 mmol, 6 equiv., 1 m in THF) for 16 h at room temperature.

The volatiles were removed under reduced pressure and the residue

was taken up in 1 m HCl (20 mL) and CH₂Cl₂(50 mL). The organic

phase was separated and the aqueous phase was extracted with

CH₂Cl₂(3ϫ50 mL). The combined organic layers were dried with

MgSO₄and the solvent was removed under reduced pressure. Flash

column chromatography (cyclohexane/ethyl acetate, 8:1) afforded

the title compound 2-CCH (35.5 mg, 65%) as a yellow solid; R_f=

0.27 (cyclohexane/ethyl acetate, 8:1); m.p. 138 °C. ¹H NMR

(400 MHz, CDCl₃): δ = 3.06 (s, 6 H, CϵCH), 7.03 (s, 4 H, 2-H, 3-

H), 7.11 (AAЈBBЈ, J = 8.4 Hz, 12 H, 2Ј-H), 7.38 (AAЈBBЈ, J =

8.4 Hz, 12 H, 3Ј-H) ppm. ¹³C NMR (100 MHz, CDCl₃): δ = 64.4

[C_q, C(Ar)₄], 77.5 (+, CϵCH), 83.2 (C_q, CϵCH), 120.1 (C_q, C-4Ј),

130.3 (+, C-2, C-3), 130.8 (+, C-2Ј), 131.5 (+, C-3Ј), 143.5 (C_q, C-

3Ј), 144.80 (C , C-1, C-4), 145.1 (C , C-1Ј) ppm. IR (DRIFT): ν =

˜

q

3430, 3057, 2922, 2847, 1914, 1659, 1580, 1561, 1483, 1447, 1393,

1317, 1277, 1192, 1068, 1004, 920, 808, 781, 758, 702, 639, 533,

507, 420 cm^–1. MS (FAB, 3-NBA): m/z (%) = 1317 (1) [M⁺], 1191

(1) [M⁺– I], 1114 (1) [M⁺– C₆H₅I], 154 (100).

4Ј-[1,4-Phenylenebis(methanetetrayl)]hexabenzenesulfonic Acid (2-

SO₃H): To a suspension of 2-H (1.50 g, 2.67 mmol, 1 equiv.) in

anhydrous CH₂Cl₂(100 mL), chlorosulfonic acid (3.2 mL, 5.59 g,

48.0 mmol, 18 equiv.) was added dropwise under vigorous stirring.

The resulting reaction mixture was heated at 35 °C for 90 min. The

supernatant yellow solution was carefully decanted and the vola-

tiles of this solution were removed under reduced pressure. The

residual solid was washed with water (250 mL) and dried in vacuo.

Without further purification, the title compound 2-SO₃H (1.28 g,

1

46%) was obtained as a yellow solid; m.p. 398 °C (dec.). H NMR

(400 MHz, [D₆]DMSO): δ = 7.05–7.10 (m, 16 H, 2-H, 3-H, 2Ј-H),

7.52 (AAЈBBЈ, 12 H, 3Ј-H), 11.15 (br. s, 6 H, SO₃H) ppm. ¹³C

NMR (100 MHz, [D₆]DMSO): δ = 63.7 [C_q, C(Ar)₄], 125.0 (+, C-

2Ј), 129.9 (+, C-2, C-3, C-3Ј), 143.5 (C_q, C-1, C-4), 145.2 (C_q, C-

4Ј), 146.5 (C , C-1Ј) ppm. IR (DRIFT): ν = 3370, 1654, 1583, 1490,

˜

q

1373, 1168, 1082, 1034, 1005, 818, 729, 700, 628, 549, 420 cm^–1.

MS (FAB, 3-NBA): m/z (%) = 1043 (1) [M + H⁺], 154 (100).

+

HRMS (FAB): calcd. for C₄₄H₃₅O₁₈S₆1043.0148; found

1043.0142.

1,4-Bis[tris(4Ј-nitrophenyl)methyl]benzene (2-NO₂): To a suspension

of 2-H (0.20 g, 0.36 mmol, 1 equiv.) in glacial acetic acid (15 mL),

nitric acid (99%, 1.0 mL) was added dropwise at 65 °C. The formed

reaction mixture was stirred for 18 h. After cooling to room tem-

perature, water was added (100 mL) and the formed precipitate was

filtered off and washed with water (200 mL). Flash column

chromatography afforded 2-NO₂(62.9 mg, 21%) as a yellow pow-

1, C-4), 146.4 (C , C-1Ј) ppm. IR (DRIFT): ν = 3230, 3033, 2925,

˜

q

2850, 2214, 2108, 1929, 1602, 1570, 1498, 1447, 1407, 1248, 1116,

1019, 825, 796, 764, 701, 651, 574, 554, 415, 450, 409 cm^–1. MS

(FAB, 3-NBA): m/z (%) = 707 (18) [M + H⁺], 706 (16) [M⁺], 605

(17) [M⁺– C₈H₅], 391 (18) [C₃₁H₁₉⁺], 315 (24) [C₂₅H₁₅⁺], 154 (100).

HRMS (FAB): calcd. for C₅₆H₃₅707.2739; found 707.2743.

1

der; R_f= 0.70 (CH₂Cl₂); m.p. 279 °C (dec.). H NMR (400 MHz,

[D₆]DMSO): δ = 7.24 (s, 4 H, 2-H, 3-H), 7.52 (AAЈBBЈ, J = 9.0 Hz, 1,4-Bis[tris(4Ј-methylphenyl)methyl]benzene (2-Me): A solution of

12 H, 2Ј-H), 8.22 (AAЈBBЈ, J = 9.0 Hz, 12 H, 3Ј-H) ppm. ¹³C 2-Br (0.25 g, 0.24 mmol, 1 equiv.) in anhydrous THF (50 mL) was

NMR (100 MHz, [D₆]DMSO): δ = 64.6 [C_q, C(Ar)₄], 123.5 (+, C- cooled to –78 °C under an argon atmosphere. At this temperature,

3Ј), 131.4 (+, C-2, C-3, C-2Ј), 145.9 (C_q, C-1, C-4, C-4Ј), 151.6 (C_q,

n-butyllithium (1.2 mL, 0.19 g, 2.89 mmol, 12 equiv., 2.5 m in hex-

ane) was added dropwise and the reaction mixture was stirred for

14 h. Methyl iodide (1.3 mL, 1.23 g, 8.69 mmol, 36 equiv.) was

C-1Ј) ppm. IR (DRIFT): ν = 2857, 1591, 1512, 1433, 1187, 1109,

˜

1066, 1013, 839, 820, 744, 705, 570, 458 cm^–1.

294

www.eurjoc.org

Eur. J. Org. Chem. 2013, 283–299

1,4-Ditrityl- and 1,3,5-Tritritylbenzene Derivatives

added dropwise and the reaction mixture was stirred for 16 h and

warmed to room temperature. The reaction mixture was diluted

with CH₂Cl₂(100 mL) and treated with satd. aqueous NH₄Cl

(50 mL). The organic phase was separated and the aqueous phase

was extracted with CH₂Cl₂(2ϫ100 mL). The combined organic

layers were dried with MgSO₄and the solvent was removed under

reduced pressure. Flash column chromatography (cyclohexane/

pended in anhydrous CH₂Cl₂(15 mL) and cooled to 0 °C. Triethyl-

amine (0.32 mL, 0.23 g, 2.28 mmol, 15 equiv.) and trifluorometh-

anesulfonic anhydride (0.40 mL, 0.64 g, 2.28 mmol, 15 equiv.) were

added and the reaction mixture was stirred for 16 h and warmed

to room temperature. The volatiles were removed under reduced

pressure and the residue was taken up in 1 m HCl (25 mL) and

CH₂Cl₂(50 mL). The organic phase was separated and the aqueous

ethyl acetate, 25:1) afforded 2-Me (86.0 mg, 55%) as a white pow- phase was extracted with CH₂Cl₂(2ϫ35 mL). The combined or-

der; R_f= 0.51 (cyclohexane/ethyl acetate, 25:1); m.p. 266 °C (dec.).

¹H NMR (400 MHz, CDCl₃): δ = 2.32 (s, 18 H, CH₃), 7.03–7.09

(m, 28 H, 2-H, 3-H, 2Ј-H, 3Ј-H) ppm. ¹³C NMR (100 MHz,

CDCl₃): δ = 20.9 (+, CH₃), 63.5 [C_q, C(Ar)₄], 127.9 (+, C-2Ј), 130.1

(+, C-2, C-3), 131.0 (+, C-3Ј), 135.2 (C_q, C-4Ј), 144.1 (C_q, C-1Ј),

ganic layers were washed with brine (50 mL), dried with MgSO₄,

and the solvent was removed under reduced pressure. Flash column

chromatography (cyclohexane/ethyl acetate, 4:1) afforded the prod-

uct 2-OTf (51.5 mg, 24%) as a white solid; R_f= 0.45 (cyclohexane/

ethyl acetate, 4:1); m.p. 190 °C (dec.). ¹H NMR (400 MHz, CDCl₃):

144.5 (C , C-1, C-4) ppm. IR (Drift): ν = 3020, 2920, 2855, 1506,

δ = 7.06 (s, 4 H, 2-H, 3-H), 7.21 (br. s, 24 H, 2Ј-H, 3Ј-H) ppm. ¹³

NMR (100 MHz, CDCl₃): δ = 63.6 [C_q, C(Ar)₄], 118.7 (C_q, J_C–F

C

=

˜

q

1447, 1376, 1191, 1119, 1021, 807, 783, 754, 703, 640, 595, 573,

527, 495, 421 cm^–1. MS (70 eV, EI): m/z (%) = 646 (9) [M⁺], 555 320.6 Hz, CF₃), 121.0 (+, C-3Ј), 130.4 (+, C-2, C-3), 132.4 (+, C-

(50) [M⁺– C₇H₇], 464 (13) [C₃₆H₃₂⁺], 285 (100) [C₂₂H₂₁⁺]. HRMS 2Ј), 145.3 (C_q, C-1Ј), 148.0 (C_q, C-1, C-4), 157.6 (C_q, C-4Ј) ppm.

(EI): calcd. for C₅₀H₄₆646.3600; found 646.3601.

IR (ATR): ν = 2927, 1611, 1497, 1422, 1348, 1249, 1203, 1134,

˜

1098, 1016, 954, 883, 827, 778, 751, 718, 639, 606, 574, 525, 500,

1,4-Bis[bis(4Ј-bromophenyl)(4ЈЈ-amino-3ЈЈ,5ЈЈ-dibromophenyl)meth-

yl]benzene (7): Compound 6 (200 mg, 0.34 mmol, 1 equiv.) was

added in small portions to bromine (0.2 mL, 0.65 g, 4.08 mmol,

12 equiv.) under vigorous stirring at room temperature. The reac-

tion mixture was stirred for 20 min and then cooled to –78 °C. Eth-

anol (15 mL) was added slowly and the reaction mixture was

warmed to room temperature. The solid was filtered off and washed

with satd. aqueous Na₂S₂O₃(100 mL) and water (100 mL). With-

out further purification, the product (410 mg, 99%) was obtained

417 cm^–1.

Syntheses of the Expanded 1,4-Ditritylbenzene Derivatives

(HPXXL)

Tris[4-(4Ј-methoxyphenylethynyl)phenyl]methanol (16): A mixture of

11-H (1.00 g, 3.00 mmol, 1 equiv.), [PdCl₂(PPh₃)₂] (147 mg,

0.21 mmol, 7 mol-%), CuI (80.0 mg, 0.42 mmol, 0.14 equiv.), and

4-iodoanisole (2.60 g, 11.3 mmol, 3.8 equiv.) was dissolved in anhy-

drous THF (7 mL) and triethylamine (14 mL). The reaction mix-

ture was stirred for 16 h at 80 °C. The solvent was removed under

reduced pressure and the residue was purified by flash column

chromatography (cyclohexane/ethyl acetate, 4:1) to yield 16 (1.41 g,

72%) as a white solid; R_f= 0.19 (cyclohexane/ethyl acetate, 3:1);

m.p. 171 °C. ¹H NMR (400 MHz, CDCl₃): δ = 3.83 (s, 9 H, OCH₃),

6.88 (AAЈBBЈ, J = 8.9 Hz, 6 H, 3Ј-H), 7.25 (AAЈBBЈ, J = 8.5 Hz,

6 H, 2-H), 7.45–7.49 (m, 12 H, 3-H, 2Ј-H) ppm. ¹³C NMR

(100 MHz, CDCl₃): δ = 55.3 (+, OCH₃), 81.6 (C_q, COH), 87.68

[C_q, CϵC-Ar(OMe)], 89.9 [C_q, CϵC-Ar(OMe)], 114.0 (+, C-3Ј),

115.2 (C_q, C-1Ј), 122.86 (C_q, C-4), 127.8 (+, C-2), 131.1 (+, C-3),

133.1 (+, C-2Ј), 145.8 (C_q, C-1), 159.7 (C_q, C-4Ј) ppm. IR

1

as a beige solid; m.p. 181 °C (dec.). H NMR (300 MHz, CDCl₃):

δ = 4.55 (s, 4 H, NH₂), 6.97–7.00 (m, 12 H, 2Ј-H, 2ЈЈ-H, 6ЈЈ-H),

7.07 (s, 4 H, 2-H, 3-H), 7.40 (AAЈBBЈ, J = 8.7 Hz, 8 H, 3Ј-H) ppm.

¹³C NMR (300 MHz, CDCl₃): δ = 62.9 [C_q, C(Ar)₄], 108.1 (C_q, C-

3ЈЈ, C-5ЈЈ), 120.8 (C_q, C-4Ј), 130.2 (+, C-2, C-3), 131.0 (+, C-2Ј),

132.4 (+, C-3Ј), 133.8 (+, C-2ЈЈ, C-6ЈЈ), 136.5 (C_q, C-1ЈЈ), 140.5 (C_q,

C-1, C-4), 143.7 (C , C-4ЈЈ), 144.5 (C , C-1Ј) ppm. IR (DRIFT): ν

˜

q

= 3476, 3376, 3085, 2591, 2130, 1928, 1612, 1570, 1536, 1473, 1394,

1302, 1265, 1243, 1147, 1078, 1009, 939, 868, 814, 733, 682, 628,

541, 523 cm^–1. MS (FAB, 3-NBA): m/z (%) = 1222 (1) [M⁺], 154

(100).

1,4-Bis[tris(4Ј-hydroxyphenyl)methyl]benzene

(2-OH):

Phenol

(DRIFT): ν = 3466, 3037, 3002, 2958, 2836, 2535, 2215, 2029, 1919,

˜

(4.12 g, 43.8 mmol, 8 equiv.) and 5-OMe (3.08 g, 5.47 mmol,

1 equiv.) was heated at 200 °C for 1 h under vigorous stirring. The

residue was diluted with CH₂Cl₂(100 mL) and cooled to 0 °C.

Boron tribromide (3.1 mL, 8.22 g, 32.8 mmol, 6 equiv.) was added

dropwise and the reaction mixture was stirred for 16 h and warmed

to room temperature. Methanol (50 mL) was added carefully at

0 °C and the volatiles were removed under reduced pressure. This

procedure was repeated five times. Flash column chromatography

(cyclohexane/ethyl acetate, 1:2) yielded the title compound 2-OH

(1.31 g, 36%) as a reddish solid; R_f= 0.28 (cyclohexane/ethyl acet-

ate, 1:2); m.p. 218 °C (dec.). ¹H NMR (400 MHz, [D₆]DMSO): δ =

6.63 (d, J = 8.8 Hz, 12 H, 3Ј-H), 6.82 (d, J = 8.8 Hz, 12 H, 2Ј-H),

6.93 (s, 4 H, 2-H, 3-H), 9.28 (s, 6 H, OH) ppm. ¹³C NMR

(100 MHz, [D₆]DMSO): δ = 61.7 [C_q, C(Ar)₄], 113.9 (+, C-3Ј),

129.2 (+, C-2, C-3), 131.3 (+, C-2Ј), 137.43 (C_q, C-1Ј), 144.7 (C_q,

1602, 1569, 1515, 1464, 1440, 1404, 1287, 1250, 1174, 1138, 1106,

1030, 909, 830, 740, 667, 643, 596, 536 cm^–1. MS (FAB; 3-NBA):

m/z (%) = 650 (14) [M⁺], 633 (23) [M⁺– OH], 443 (14) [M⁺

–

C₁₅H₁₁O], 235 (46) [C₁₆H₁₁O₂⁺], 154 (100). HRMS (FAB): calcd.

for C₄₆H₃₄O₄651.2535; found 651.2533.

4ЈЈ-{Tris[4-(4Ј-methoxyphenylethynyl)phenyl]methyl}phenol

(17-

OH): A mixture of 16 (0.13 g, 0.20 mmol, 1 equiv.) and phenol

(0.28 g, 3.00 mmol, 15 equiv.) was heated at 120 °C for 14 h. The

reaction solution was diluted with CH₂Cl₂(20 mL) and washed

with 1 m NaOH (2ϫ10 mL) and water (15 mL). The organic layer

was dried with MgSO₄and the solvent was removed under reduced

pressure. Flash column chromatography (cyclohexane/ethyl acetate,

4:1) afforded 17-OH (69.5 mg, 58%) as a yellow oil; R_f= 0.12 (cy-

clohexane/ethyl acetate, 4:1). ¹H NMR (400 MHz, CDCl₃): δ = 3.82

(s, 9 H, OCH₃), 6.74 (AAЈBBЈ, J = 8.8 Hz, 2 H, 3ЈЈ-H), 6.88

(AAЈBBЈ, J = 8.9 Hz, 6 H, 3Ј-H), 7.04 (AAЈBBЈ, J = 8.8 Hz, 2 H,

2ЈЈ-H), 7.17 (AAЈBBЈ, J = 8.6 Hz, 6 H, 2-H), 7.41 (AAЈBBЈ, J =

C-1, C-4), 154.9 (C , C-4Ј) ppm. IR (DRIFT): ν = 3372, 1699,

˜

q

1610, 1507, 1436, 1364, 1232, 1178, 1112, 1016, 827, 600, 578, 541,

449 cm^–1. MS (70 eV, EI): m/z (%) = 658 (18) [M⁺], 565 (42) [M⁺

–

8.6 Hz, 6 H, 3-H), 7.47 (AAЈBBЈ, J = 8.9 Hz, 6 H, 2Ј-H) ppm. ¹³

C

C₆H₅O], 472 (8) [M⁺– C₁₂H₁₀O₂], 367 (6) [C₂₅H₁₉O₃⁺], 291 (75)

[C₁₉H₁₅O₃⁺], 133 (100). HRMS (EI): calcd. for C₄₄H₃₄O₆658.2368;

found 658.2355.

NMR (100 MHz, CDCl₃): δ = 55.3 (+, OCH₃), 64.1 [C_q, C(Ar)₄],

87.8 [C_q, CϵC-Ar(OMe)], 89.6 [C_q, CϵC-Ar(OMe)], 114.0 (+, C-

3Ј), 114.6 (+, C-3ЈЈ), 115.3 (C_q, C-1Ј), 121.3 (C_q, C-4), 130.7 (+, C-

(2- 2), 130.9 (+, C-3), 132.2 (+, C-2ЈЈ), 133.1 (+, C-2Ј), 138.0 (C_q, C-

1ЈЈ), 146.3 (C_q, C-1), 153.9 (C_q, C-4ЈЈ), 159.6 (C_q, C-4Ј) ppm. IR

1,4-Bis[tris(4Ј-trifluoromethylsulfonylphenyl)methyl]benzene

OTf): Compound 2-OH (100 mg, 0.15 mmol, 1 equiv.) was sus-

Eur. J. Org. Chem. 2013, 283–299

www.eurjoc.org

295

T. Muller, S. Bräse et al.

FULL PAPER

(DRIFT): ν = 3358, 2925, 2537, 2214, 2031, 1890, 1686, 1604, 1513,

[C_q, C(Ar)₄], 79.9 (C_q, CϵCH), 83.8 (+, CϵCH), 87.3 [C_q, CϵC-

Ar(OMe)], 89.5 [C_q, CϵC-Ar(OMe)], 113.7 (+, C-3Ј), 114.9 (C_q,

C-1Ј), 119.8 (C_q, C-4, C-4ЈЈ), 131.0 (+, C-2, C-2ЈЈ), 132.8 (+, C-3,

˜

1464, 1287, 1249, 1175, 1138, 1107, 1029, 910, 829, 737, 666, 643,

591, 526 cm^–1. MS (70 eV, EI): m/z (%) = 726 (11) [M⁺], 633 (7)

[M⁺– C₆H₅O], 519 (23) [M⁺– C₁₅H₁₁O], 221 (28) [C₁₆H₁₃O⁺], C-3ЈЈ, C-2Ј), 145.1 (C_q, C-1, C-1ЈЈ), 159.3 (C_q, C-4Ј) ppm. IR

207 (40) [C₁₅H₁₁O⁺], 133 (100). HRMS (EI): calcd. for C₅₂H₃₈O₄(DRIFT): ν = 2923, 2852, 2212, 1725, 1603, 1568, 1511, 1463, 1439,

˜

726.2770; found 726.2767.

1286, 1246, 1173, 1138, 1106, 1028, 886, 820, 742, 722, 692, 664,

639, 596, 517 cm^–1.

4ЈЈ-{Tris[4-(4Ј-methoxyphenylethynyl)phenyl]methyl}phenyltrifluoro-

methanesulfonate (17-OTf): Compound 17-OH (455 mg,

0.63 mmol, 1 equiv.) was suspended in anhydrous pyridine (15 mL)

and cooled to 0 °C. Trifluoromethanesulfonic anhydride (0.13 mL,

220 mg, 0.75 mmol, 1.2 equiv.) was added dropwise and the reac-

tion mixture was stirred for 16 h and warmed to room temperature.

The reaction was quenched with satd. aqueous NH₄Cl (25 mL) and

water (25 mL) and the aqueous reaction mixture was extracted with

CH₂Cl₂(3ϫ50 mL). The combined organic layers were dried with

MgSO₄and the solvent was removed under reduced pressure. Flash

column chromatography (cyclohexane/ethyl acetate, 7:2) afforded

product 17-OTf (330 mg, 61%) as a light-brown oil; R_f= 0.08 (cy-

clohexane/ethyl acetate, 25:1). ¹H NMR (400 MHz, CDCl₃): δ =

3.83 (s, 9 H, OCH₃), 6.88 (AAЈBBЈ, J = 8.9 Hz, 6 H, 3Ј-H), 7.14

(AAЈBBЈ, J = 8.7 Hz, 6 H, 2-H), 7.19 (AAЈBBЈ, J = 9.0 Hz, 2 H,

2ЈЈ-H), 7.31 (AAЈBBЈ, J = 9.0 Hz, 2 H, 3ЈЈ-H), 7.44 (AAЈBBЈ, J =

1,4-Bis[1Ј-ethynyl-4Ј-tri(4ЈЈЈ-methoxytolanyl)methyl]benzene

(9-

OMe): A mixture of 17-CCH (70.0 mg, 95.3 μmol, 2.5 equiv.),

[PdCl₂(PPh₃)₂] (2.1 mg, 3.05 μmol, 8 mol-%), CuI (1.2 mg,

6.09 μmol, 0.16 equiv.), and 1,4-diiodobenzene (12.6 mg,

38.2 μmol, 1 equiv.) in anhydrous THF (0.75 mL) and triethyl-

amine (2.5 mL) was heated to 60 °C for 16 h under an argon atmo-

sphere. The solvents were removed under reduced pressure and the

residue was purified by flash column chromatography (cyclohex-

ane/ethyl acetate, 2:1). The title compound 9-OMe (21.8 mg, 37%)

was obtained as a beige solid; R_f= 0.21 (cyclohexane/ethyl acetate,

1

2:1). H NMR (400 MHz, CDCl₃): δ = 3.83 (s, 18 H, OCH₃), 6.87

(AAЈBBЈ, J = 8.9 Hz, 12 H, 3ЈЈЈ-H), 7.14–7.21 (m, 16 H, 2Ј-H, 2ЈЈ-

H), 7.40–7.50 (m, 32 H, 2-H, 3-H, 2ЈЈЈ-H, 3Ј-H, 3ЈЈ-H) ppm. ¹³C

NMR (100 MHz, CDCl₃): δ = 55.3 (+, OCH₃), 64.8 [C_q, C(Ar)₄],

87.6 [C_q, CϵC(C-1)], 87.7 [C_q, CϵC(C-4Ј)], 89.8 [C_q, CϵC(C-4Ј)],

89.8 [C_q, CϵC(C-1)], 114.0 (+, C-3ЈЈЈ), 115.3 (C_q, C-1ЈЈЈ), 121.6

(C_q, C-1, C-4, C-4Ј, C-4ЈЈ), 130.9 (+, C-2, C-3, C-2Ј, C-2ЈЈ), 133.1

(+, C-3Ј, C-3ЈЈ, C-2ЈЈЈ), 145.6 (C_q, C-1Ј, C-1ЈЈ), 159.6 (C_q, C-

8.7 Hz, 6 H, 3-H), 7.47 (AAЈBBЈ, J = 8.9 Hz, 6 H, 2Ј-H) ppm. ¹³

C

NMR (100 MHz, CDCl₃): δ = 55.3 (+, OCH₃), 64.5 [C_q, C(Ar)₄],

87.5 [C_q, CϵC-Ar(OMe)], 90.0 [C_q, CϵC-Ar(OMe)], 114.0 (+, C-

3Ј), 115.2 (C_q, C-1Ј), 118.7 (C_q, J_C,F= 318.7 Hz, CF₃), 120.5 (C_q,

C-4), 121.9 (+, C-3ЈЈ), 130.74 (+, C-3), 131.0 (+, C-2), 132.7 (+, C-

2ЈЈ), 133.1 (+, C-2Ј), 145.2 (C_q, C-1), 146.4 (C_q, C-1ЈЈ), 147.8 (C_q,

4ЈЈЈ) ppm. IR (DRIFT): ν = 3035, 2999, 2927, 2853, 2538, 2214,

˜

2031, 1920, 1727, 1605, 1568, 1514, 1464, 1441, 1412, 1287, 1249,

1174, 1139, 1107, 1073, 1030, 958, 828, 742, 724, 693, 667,

528 cm^–1.

C-4ЈЈ), 159.7 (C , C-4Ј) ppm. IR (DRIFT): ν = 3037, 2999, 2933,

˜

q

2839, 2537, 2214, 2032, 1889, 1660, 1604, 1569, 1514, 1465, 1424,

1287, 1249, 1215, 1174, 1140, 1078, 1030, 888, 828, 753, 666, 641,

608, 575, 521, 416 cm^–1. MS (70 eV, EI): m/z (%) = 859 (64) [M⁺],

651 (100) [M⁺– C₁₅H_{1 1}O], 633 (28) [M⁺– C₇H₄F₃O₃S].

HRMS (EI): calcd. for C₅₃H₃₈F₃O₆S 859.2341; found 859.2339.

Synthesis of 1,3,5-Tritritylbenzene Derivatives

1,3,5-Tris(diphenylhydroxymethyl)benzene (21-H): Phenyllithium

(55 mL, 9.33 g, 111 mmol, 7 equiv., 2 m in butyl ether) was diluted

with anhydrous THF (200 mL) and cooled to –78 °C under an ar-

gon atmosphere. A solution of trimethyl 1,3,5-benzenetricarb-

oxylate (20; 4.00 g, 15.9 mmol, 1 equiv.) in anhydrous THF (40 mL)

was added dropwise and the reaction mixture was stirred at –78 °C

for 4 h and then warmed to room temperature over a period of

19 h. The reaction mixture was concentrated under reduced pres-

sure and the residue was taken up in CH₂Cl₂(100 mL) and satd.

aqueous NH₄Cl (100 mL) and stirred for 30 min. The organic layer

was separated, dried with MgSO₄and the solvent was removed

under reduced pressure. Flash column chromatography (cyclohex-

ane/ethyl acetate, 3:2) afforded 21-H (9.00 g, 91%) as a light-yellow

solid; R_f= 0.35 (cyclohexane/ethyl acetate, 1:1); m.p. 191 °C. ¹H

NMR (400 MHz, [D₆]DMSO): δ = 6.26 (s, 3 H, OH), 7.05–7.11

(m, 15 H, 2-H, 4-H, 6-H, 2Ј-H), 7.15–7.22 (m, 18 H, 3Ј-H, 4Ј-

H) ppm. ¹³C NMR (100 MHz, [D₆]DMSO): δ = 80.6 (Cq, COH),

126.1 (+, C-2, C-4, C-6), 126.3 (+, C-4Ј), 127.2 (+, C-2Ј), 127.57 (+,

4ЈЈ-{Tris[4-(4Ј-methoxyphenylethynyl)phenyl]methyl}phenylacetylene

(17-CCH): A mixture of 17-OTf (0.31 g, 0.36 mmol, 1 equiv.),

[PdCl₂(PPh₃)₂] (12.6 mg, 17.9 μmol, 5 mol-%), CuI (6.9 mg,

36.2 μmol, 0.10 equiv.), and trimethylsilylacetylene (0.12 mL,

81.8 mg, 0.72 mmol, 2 equiv.) in anhydrous THF (2.5 mL) and tri-

ethylamine (5 mL) was stirred at 60 °C for 16 h under an argon

atmosphere. The volatiles were removed under reduced pressure

and the residue was taken up in CH₂Cl₂(50 mL) and water

(35 mL). The organic layer was separated, dried with MgSO₄and

the solvent was removed under reduced pressure. Flash column

chromatography (cyclohexane/ethyl acetate, 9:1) afforded the tri-

methylsilyl-protected acetylene compound 17-CCTMS (95.0 mg,

31%), which was directly desilylated.

Compound 17-CCTMS was dissolved in CH₂Cl₂(25 mL) and

methanol (50 mL) and treated with potassium fluoride (18.0 mg,

0.33 mmol, 3 equiv.) for 16 h at room temperature. The solvents

were removed under reduced pressure and the residue was taken

up in CH₂Cl₂(25 mL) and water (25 mL). The organic layer was

separated and the aqueous layer was extracted with CH₂Cl₂

(2ϫ25 mL). The combined organic layers were dried with MgSO₄

and the solvent was removed under reduced pressure. Without fur-

ther purification, the title compound 17-CCH (78.0 mg, 99%) was

obtained as a yellow solid; R_f= 0.18 (cyclohexane/ethyl acetate,

C-3Ј), 145.5 (C , C-1, C-3, C-5), 147.8 (Cq, C-1Ј) ppm. IR (ATR): ν

˜

q

= 3561, 3440, 3023, 1596, 1489, 1445, 1374, 1307, 1160, 1032, 1001,

924, 883, 853, 766, 727, 697, 647, 630, 598, 582, 426 cm^–1. MS

(FAB, 3-NBA): m/z (%) = 624 (5) [M⁺], 607 (100) [M⁺– OH], 590

(3) [M⁺– 2ϫOH], 547 [M⁺– C₆H₅], 441 (2) [M⁺– C₁₃H₁₁O],

425 (5) [M⁺– C₁₃H₁₁O₂], 183 (14) [C₁₃H₁₁O⁺], 105 (65) [C₇H₅O⁺].

1,3,5-Tris[(4ЈЈ-aminophenyldiphenyl)methyl]benzene (22-NH₂): To a

solution of aniline (1.31 mL, 1.34 g, 14.4 mmol, 9 equiv.), concd.

HCl (1.5 mL), and glacial acetic acid (6 mL), 21-H (1.00 g,

1.60 mmol, 1 equiv.) was added. The reaction mixture was heated

at 145 °C for 24 h. After cooling to room temperature, the formed

1

10:1); m.p. 67 °C. H NMR (400 MHz, CDCl₃): δ = 3.07 (s, 1 H,

CϵCH), 3.83 (s, 9 H, OCH₃), 6.87 (AAЈBBЈ, J = 8.9 Hz, 6 H, 3Ј-

H), 7.16 (AAЈBBЈ, J = 8.7 Hz, 8 H, 2-H, 2ЈЈ-H), 7.41 (AAЈBBЈ, J solid was filtered off and washed with glacial acetic acid (70 mL),

= 8.7 Hz, 8 H, 3-H, 3ЈЈ-H), 7.46 (AAЈBBЈ, J = 8.9 Hz, 6 H, 2Ј- water (70 mL), and diethyl ether (50 mL) successively. Drying in

H) ppm. ¹³C NMR (100 MHz, CDCl₃): δ = 55.0 (+, OCH₃), 64.4 vacuo afforded the title compound 22-NH₂(1.20 g, 93%) as a grey

296

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Eur. J. Org. Chem. 2013, 283–299

1,4-Ditrityl- and 1,3,5-Tritritylbenzene Derivatives

solid; m.p. 237 °C (dec.). ¹H NMR (400 MHz, [D₆]DMSO): δ = (75 mL) and ice/satd. aqueous NH₄Cl (100 mL). The organic layer

6.78–6.90 (m, 21 H, 2-H, 4-H, 6-H, 2Ј-H, 3ЈЈ-H), 6.93 (AAЈBBЈ, J was separated and the aqueous layer was extracted with CH₂Cl₂

= 8.6 Hz, 6 H, 2ЈЈ-H), 7.08–7.21 (m, 18 H, 3Ј-H, 4Ј-H) ppm. ¹³C

(3ϫ75 mL). The combined organic layers were dried with MgSO₄

NMR (100 MHz, [D₆]DMSO): δ = 64.0 [C_q, C(Ar)₄], 119.2 (+, C- and the solvent was removed under reduced pressure. Flash column

3ЈЈ), 125.6 (+, C-4Ј), 127.6 (+, C-3Ј), 129.3 (+, C-2, C-4, C-6), 129.8 chromatography (cyclohexane/ethyl acetate, 3:2) afforded the title

(+, C-2Ј), 130.5 (+, C-2ЈЈ), 135.0 (C_q, C-1ЈЈ), 141.6 (C_q, C-4ЈЈ), compound 21-OMe (2.23 g, 70%) as a yellowish solid; R_f= 0.32

144.8 (C , C-1, C-3, C-5), 146.0 (C , C-1Ј) ppm. IR (ATR): ν =

2813, 2577, 1590, 1505, 1493, 1444, 1323, 1213, 1186, 1160, 1084,

1034, 1021, 1004, 868, 821, 770, 759, 745, 723, 704, 658, 629, 577,

(cyclohexane/ethyl acetate, 1:1); m.p. 93 °C. ¹H NMR (400 MHz,

CDCl₃): δ = 2.69 (s, 3 H, OH), 3.77 (s, 18 H, OCH₃), 6.71 (AAЈBBЈ,

J = 8.9 Hz, 12 H, 3Ј-H), 7.01 (AAЈBBЈ, J = 8.9 Hz, 12 H, 2Ј-H),

˜

q

532, 514, 489, 420 cm^–1. MS (FAB, 3-NBA): m/z (%) = 850 (55) [M 7.08 (s, 3 H, 2-H, 4-H, 6-H) ppm. ¹³C NMR (100 MHz, CDCl₃): δ

+ H⁺], 772 (30) [M⁺– C₆H₅], 757 (43) [M⁺– C₆H₆N], 258 (100) = 55.2 (+, OCH₃), 81.5 (C_q, COH), 113.0 (+, C-3Ј), 126.2 (+, C-2,

[C₁₉H₁₆N⁺], 180 (47) [C₁₃H₁₀N⁺]. HRMS (FAB): calcd. for

C₆₃H₅₂N₃850.4161; found 850.4157.

C-4, C-6), 128.9 (+, C-2Ј), 139.2 (C_q, C-1Ј), 146.3 (C_q, C-1, C-3,

C-5), 158.4 (C , C-4Ј) ppm. IR (DRIFT): ν = 3485, 3036, 3000,

˜

q

2836, 2548, 2295, 2039, 1896, 1765, 1608, 1582, 1509, 1462, 1441,

1414, 1299, 1251, 1176, 1116, 1034, 925, 873, 832, 786, 746, 719,

701, 638, 606, 581, 413 cm^–1. MS (FAB, 3-NBA): m/z (%) = 804

(11) [M⁺], 787 (100) [M⁺– OH], 770 (5) [M⁺– 2ϫOH], 697 (10)

[M⁺– C₇H₇O], 679 (9) [M⁺– C₇H₇O₂], 651 (6) [M⁺– C₇H₇O₃],

544 (17) [C₃₆H₃₂O₅⁺], 243 (13) [C₁₅H₁₅O₃⁺], 107 (100) [C₇H₇O⁺].

HRMS (FAB): calcd. for C₅₁H₄₉O₈804.3298; found 804.3295.

1,3,5-Tritritylbenzene (3-H): Compound 22-NH₂(1.00 g,

1.20 mmol, 1 equiv.) was suspended in glacial acetic acid (100 mL)

and hypophosphoric acid (10 mL, 50% aqueous solution). Under

vigorous stirring, sodium nitrite (6.20 g, 90.0 mmol, 38 equiv.) was

added in small portions. The reaction mixture was stirred for 24 h

at room temperature. Water (50 mL) was added to complete the

precipitation. The formed solid was filtered off and washed with

glacial acetic acid (50 mL), water (150 mL) and diethyl ether

(25 mL). Drying in vacuo gave 3-H (0.88 g, 91%) as a beige solid;

1,3,5-Tris[tris(4Ј-hydroxyphenyl)methyl]benzene (3-OH): A mixture

of 21-OMe (1.00 g, 1.24 mmol, 1 equiv.) and phenol (3.51 g,

12.4 mmol, 10 equiv.) in glacial acetic acid (5 mL) were heated at

140 °C for 12 h. The solvent was removed under reduced pressure

and the residue was taken up in CH₂Cl₂(20 mL) and cooled to 0 °C

under an argon atmosphere. Boron tribromide (0.51 mL, 1.34 g,

5.34 mmol, 12 equiv.) was added dropwise and the reaction mixture

was stirred for 16 h and warmed to room temperature. Methanol

(30 mL) was added carefully at 0 °C and the volatiles were removed

under reduced pressure. This procedure was repeated four times.

Flash column chromatography (cyclohexane/ethyl acetate, 1:10) af-

forded the product 3-OH (0.26 g, 22%) as a reddish solid; R_f=

0.19 (cyclohexane/ethyl acetate, 1:10); m.p. 216 °C. ¹H NMR

(400 MHz, [D₆]DMSO): δ = 6.50 (AAЈBBЈ, J = 8.8 Hz, 18 H, 3Ј-

H), 6.62 (AAЈBBЈ, J = 8.8 Hz, 18 H, 2Ј-H), 6.83 (s, 3 H, 2-H, 4-H,

6-H), 9.16 (s, 9 H, OH) ppm. ¹³C NMR (100 MHz, [D₆]DMSO): δ

= 62.3 [C_q, C(Ar)₄], 113.9 (+, C-3Ј), 130.11 (+, C-2, C-4, C-6),

130.9 (+, C-2Ј), 137.7 (C_q, C-1Ј), 145.0 (C_q, C-1, C-3, C-5), 154.5

1

R_f= 0.23 (cyclohexane/ethyl acetate, 25:1); m.p. 282 °C (dec.). H

NMR (400 MHz, CDCl₃): δ = 6.93 (s, 3 H, 2-H, 4-H, 6-H), 6.94–

7.00 (m, 18 H, 2Ј-H), 7.06–7.13 (m, 27 H, 3Ј-H, 4Ј-H) ppm. ¹³C

NMR (100 MHz, CDCl₃): δ = 65.0 [C_q, C(Ar)₄], 125.4 (+, C-4Ј),

127.4 (+, C-3Ј), 130.7 (+, C-2Ј), 131.5 (+, C-2, C-4, C-6), 145.2

(C , C-1, C-3, C-5), 146.7 (C , C-1Ј) ppm. IR (ATR): ν = 3054,

˜

q

2923, 1739, 1591, 1490, 1441, 1371, 1236, 1084, 1034, 913, 843,

763, 752, 697, 644, 629, 531, 507, 488 cm^–1. MS (FAB, 3-NBA):

m/z (%) = 804 (6) [M⁺], 727 (10) [M⁺– C₆H₅], 243 (25) [C₁₉H₁₅⁺],

81 (100). HRMS (FAB): calcd. for C₆₃H₄₈804.3756; found

804.3759.

1,3,5-Tris[(4ЈЈ-hydroxyphenyldiphenyl)methyl]benzene (22-OH):

A

mixture of 21-H (0.20 g, 0.32 mmol, 1 equiv.) and phenol (0.60 g,

6.40 mmol, 20 equiv.) in glacial acetic acid (1 mL) was heated at

160 °C for 16 h. After cooling to room temperature, the crude prod-

uct was purified by flash column chromatography (cyclohexane/

ethyl acetate, 2:1) to give the title compound 22-OH (117 mg, 43%)

as a yellowish solid; R_f= 0.46 (cyclohexane/ethyl acetate, 1:1); m.p.

(C , C-4Ј) ppm. IR (DRIFT): ν = 3874, 3349, 3031, 2799, 2707,

˜

q

2490, 2073, 1900, 1774, 1699, 1609, 1595, 1507, 1437, 1360, 1234,

1177, 1112, 1043, 1015, 947, 903, 872, 831, 744, 722, 686, 628, 601,

577, 524, 494, 414, 405 cm^–1. MS (FAB, 3-NBA): m/z (%) = 948

(10) [M⁺], 855 (12) [M⁺– C₆H₅O], 289 (8) [C₄₄H₃₃O₆⁺], 154 (100).

HRMS (FAB): calcd. for C₆₃H₄₈O₉948.3298; found 948.3295.

1

226 °C (dec.). H NMR (400 MHz, CDCl₃): δ = 6.54 (AAЈBBЈ, J

= 8.8 Hz, 6 H, 3ЈЈ-H), 6.78 (AAЈBBЈ, J = 8.8 Hz, 6 H, 2ЈЈ-H), 6.83

(s, 3 H, 2-H, 4-H, 6-H), 6.93–7.08 (m, 12 H, 2Ј-H), 7.06–7.11 (m,

18 H, 3Ј-H, 4Ј-H) ppm. ¹³C NMR (100 MHz, CDCl₃): δ = 64.3

[C_q, C(Ar)₄], 114.2 (+, C-3ЈЈ), 125.4 (+, C-4Ј), 127.3 (+, C-3Ј), 130.6

(+, C-2Ј), 131.4 (+, C-2, C-4, C-6), 131.9 (+, C-2ЈЈ), 139.2 (C_q, C-

1ЈЈ), 145.4 (C_q, C-1, C-3, C-5), 146.9 (C_q, C-1Ј), 153.0 (C_q, C-

1,3,5-Tris[tris(4Ј-trifluoromethylsulfonylphenyl)methyl]benzene (3-

OTf): A suspension of 3-OH (100 mg, 0.11 mmol, 1 equiv.) in anhy-

drous CH₂Cl₂(15 mL) was cooled to 0 °C. 2,6-Lutidine (0.28 mL,

0.25 g, 2.37 mmol, 23 equiv.) and trifluoromethanesulfonic anhy-

dride (0.39 mL, 0.67 g, 2.37 mmol, 23 equiv.) were added and the

reaction mixture was stirred for 24 h and warmed to room tempera-

ture over this period. The volatiles were removed under reduced

pressure and the residue was taken up in CH₂Cl₂(100 mL). The

organic phase was washed with 2 m HCl (2ϫ50 mL), water

(50 mL), and brine (50 mL), dried with MgSO₄and the solvent was

removed under reduced pressure. Flash column chromatography

(cyclohexane/ethyl acetate, 5:1) afforded the title compound 3-OTf

(96.0 mg, 41%) as a brownish solid; R_f= 0.34 (cyclohexane/ethyl

4ЈЈ) ppm. IR (ATR): ν = 3373, 3054, 2918, 2850, 1592, 1506, 1490,

˜

1441, 1235, 1177, 1111, 1033, 1013, 907, 867, 830, 759, 732, 701,

631, 581, 530, 426 cm^–1. MS (FAB, 3-NBA): m/z (%) = 852 (10)

[M⁺], 775 (29) [M⁺– C₆H₅], 759 [M⁺– C₆H₆O], 698 (1), [M⁺

–

C₁₂H₁₀], 647 (21) [C₅₁H₃₅⁺], 259 (100) [C₁₉H₁₅O⁺]. HRMS (FAB):

calcd. for C₆₃H₄₈O₃852.3603; found 852.3607.

Benzene-1,3,5-tris[bis(4Ј-methoxyphenyl)methanol] (21-OMe):

A

solution of 4-bromoanisole (4.00 mL, 5.93 g, 31.7 mmol, 8 equiv.)

in anhydrous THF (100 mL) was cooled to –78 °C under an argon

atmosphere and treated with n-butyllithium (12.7 mL, 2.03 g,

31.7 mmol, 8 equiv., 2.5 m in hexane) for 1 h. A solution of 20

(1.00 g, 3.96 mmol, 1 equiv.) in anhydrous THF (15 mL) was added

dropwise, the reaction mixture was stirred at –78 °C for 3 h and

then warmed to room temperature over a period of 16 h. The sol-

vent was evaporated and the residue was taken up in CH₂Cl₂

1

acetate, 5:1); m.p. 214 °C. H NMR (400 MHz, CDCl₃): δ = 6.69

(s, 3 H, 2-H, 4-H, 6-H), 6.92 (AAЈBBЈ, J = 9.0 Hz, 18 H, 2Ј-H),

7.12 (AAЈBBЈ, J = 9.0 Hz, 18 H, 3Ј-H) ppm. ¹³C NMR (100 MHz,

CDCl₃): δ = 64.0 [C_q, C(Ar)₄], 118.6 (C_q, J_C–F= 320.5 Hz, CF₃),

121.3 (+, C-3Ј), 131.2 (+, C-2, C-4, C-6), 131.8 (+, C-2Ј), 144.7

(C_q, C-1Ј), 145.5 (C_q, C-1, C-3, C-5), 147.9 (C_q, C-4Ј) ppm. IR

Eur. J. Org. Chem. 2013, 283–299

www.eurjoc.org

297

T. Muller, S. Bräse et al.

FULL PAPER

(ATR): ν = 3561, 3440, 3023, 1596, 1489, 1445, 1374, 1307, 1160,

4,4Ј,4ЈЈ,4ЈЈЈ,4ЈЈЈЈ,4ЈЈЈЈЈ,4ЈЈЈЈЈЈ,4ЈЈЈЈЈЈЈ,4ЈЈЈЈЈЈЈЈ-[Benzene-1,3,5-triyl-

tris(methanetetrayl)]nonabenzenesulfonic Acid (3-SO₃H): To a sus-

˜

1032, 1001, 924, 883, 853, 766, 727, 697, 647, 630, 598, 582,

426 cm^–1. MS (FAB, 3-NBA): m/z (%) = 2139 (11) [M + H⁺], 1912 pension of 3-H (50.0 mg, 62.1 μmol, 1 equiv.) in anhydrous CH₂Cl₂

(10) [M + H⁺– C₇H₄F₃O₃S], 1686 (8) [M + H⁺– C₁₄H₈F₆O₆S₂], (5 mL), chlorosulfonic acid (0.11 mL, 195 mg, 1.68 mmol,

687 (31) [C₂₂H₁₂F₉O₉S₃⁺], 95 (100) [CH₃O₃S⁺].

27 equiv.) was added dropwise and the reaction mixture was heated

at 35 °C for 12 h. The supernatant solution was decanted and the

solvent was removed under reduced pressure. The oily residue was

taken up in water (10 mL) and the formed solid was filtered off

and washed with water (75 mL). Drying in vacuo gave the title

1,3,5-Tris[tris(4Ј-bromophenyl)methyl]benzene (3-Br): Compound 3-

H (200 mg, 0.25 mmol, 1 equiv.) was added in small portions to

bromine (0.45 mL, 1.34 g, 8.40 mmol, 27 equiv.) under vigorous

stirring. The reaction mixture was stirred for 1 h at room tempera-

ture and then cooled to –78 °C. Ethanol (15 mL) was added and

the reaction mixture was warmed to room temperature. The solid

was filtered off and washed with satd. aqueous Na₂S₂O₃(50 mL),

water (125 mL), and ethanol (25 mL). Drying in vacuo yielded 3-

Br (315 mg, 83%) as a yellow solid; R_f= 0.59 (cyclohexane/ethyl

1

compound 3-SO₃H (36.0 mg, 38%) as a yellowish solid. H NMR

(400 MHz, [D₆]DMSO): δ = 6.99 (AAЈBBЈ, J = 8.3 Hz, 18 H, 2Ј-

H), 7.13 (s, 3 H, 2-H, 4-H, 6-H), 7.47 (AAЈBBЈ, J = 8.3 Hz, 18 H,

3Ј-H) ppm. ¹³C NMR (100 MHz, [D₆]DMSO): δ = 64.7 [C_q,

C(Ar)₄], 125.3 (+, C-2, C-4, C-6, C-3Ј), 129.3 (+, C-2Ј), 144.0 (C_q,

C-4Ј), 144.9 (C_q, C-1, C-3, C-5), 147.0 (C_q, C-1Ј) ppm.

1

acetate, 25:1); m.p. 166 °C. H NMR (400 MHz, CDCl₃): δ = 6.69

Supporting Information (see footnote on the first page of this arti-

cle): Synthetic procedures of HPX and HPXXL precursors, copies

of NMR spectra, crystallographic data.

(s, 3 H, 2-H, 4-H, 6-H), 6.71 (AAЈBBЈ, J = 8.7 Hz, 18 H, 2Ј-H),

7.28 (AAЈBBЈ, J = 8.7 Hz, 18 H, 3Ј-H) ppm. ¹³C NMR (100 MHz,

CDCl₃): δ = 64.0 [C_q, C(Ar)₄], 120.6 (C_q, C-4Ј), 131.0 (+, C-2Ј),

131.2 (+, C-2, C-4, C-6), 131.9 (+, C-3Ј), 144.2 (C_q, C-1Ј), 145.1

(C , C-1, C-3, C-5) ppm. IR (ATR): ν = 2923, 1774, 1585, 1482,

˜

q

Acknowledgments

1435, 1395, 1188, 1076, 1007, 870, 811, 740, 674, 656, 627, 534,

502, 422 cm^–1. MS (FAB, 3-NBA): m/z (%) = 1511/1513/1515/1517/

1519/1521 (3/4/5/4/3/2) [M⁺], 1352/1354/1356/1358/1360/1362/1364

(1/4/8/13/9/5/1) [M⁺– C₆H₄Br], 1274/1276/1278/1280/1282/1284

(1/2/3/3/2/2) [M⁺– C₆H₄Br₂], 477/479/481 (14/47/12) [C₁₉H₁₂Br₃⁺].

This work was supported by the DFG Center for Functional Nano-

structures (CFN, C5.2 and E1.1). O. P. was a fellow of the Konrad-

Adenauer-Stiftung.

1,3,5-Tris[tris(4Ј-iodophenyl)methyl]benzene (3-I): A mixture of 3-H

(200 mg, 0.25 mmol, 1 equiv.), iodine (0.76 g, 3.00 mmol,

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12 equiv.),

and

[bis(trifluoroacetoxy)iodo]benzene

(1.08 g,

2.50 mmol, 10 equiv.) was suspended in carbon tetrachloride

(15 mL) and heated to 80 °C for 24 h. The solvent was removed

under reduced pressure. Flash column chromatography (cyclohex-

aneǞcyclohexane/ethyl acetate, 20:1) afforded the title compound

3-I (69.7 μg, 28%) as a yellow solid; R_f= 0.35 (cyclohexane/ethyl

acetate, 20:1); m.p. 108 °C (dec.). ¹H NMR (400 MHz, [D₆]-

DMSO): δ = 6.56–6.64 (m, 21 H, 2-H, 4-H, 6-H, 2Ј-H), 7.57

(AAЈBBЈ, J = 8.1 Hz, 8 H, 3Ј-H) ppm. ¹³C NMR (100 MHz, [D₆]-

DMSO): δ = 63.7 [C_q, C(Ar)₄], 92.7 (C_q, C-4Ј), 129.5 (+, C-2, C-

4, C-6), 131.9 (+, C-2Ј), 136.68 (+, C-3Ј), 139.2 (C_q, C-1Ј), 144.6

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84–93.

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(C , C-1, C-3, C-5) ppm. IR (ATR): ν = 2919, 2846, 1911, 1702,

˜

q

1656, 1579, 1479, 1437, 1391, 1314, 1191, 1066, 1002, 869, 808, 735,

701, 670, 665, 651, 627, 531, 498, 434 cm^–1. MS (FAB, 3-NBA): m/z

(%) = 1937 (1) [M⁺], 1734 [M⁺– C₆H₄I], 621 (2) [C₁₉H₁₂I₃⁺], 154

(100).

1,3,5-Tris[tris(4Ј-nitrophenyl)methyl]benzene (3-NO₂): Compound

3-H (1.00 g, 1.55 mmol, 1 equiv.) was added in small portions to

nitric acid (96%, 7.5 mL) at –5 °C under vigorous stirring. The

reaction mixture was stirred for 4 h and warmed to room tempera-

ture. Glacial acetic acid (15 mL) and acetic anhydride (2.5 mL)

were added and the reaction mixture was stirred for an additional

16 h. The formed solid was filtered off, washed with water

(100 mL), and dried in vacuo. Without further purification, the title

compound 3-NO₂(1.13 g, 60%) was obtained as a bright-yellow

solid; m.p. 258 °C (decomposition). ¹H NMR (400 MHz, [D₆]-

DMSO): δ = 6.95 (s, 3 H, 2-H, 4-H, 6-H), 7.52 (AAЈBBЈ, J =

9.0 Hz, 18 H, 2Ј-H), 8.11 (AAЈBBЈ, J = 9.0 Hz, 18 H, 3Ј-H) ppm.

¹³C NMR (100 MHz, [D₆]DMSO): δ = 65.5 [C_q, C(Ar)₄], 123.4 (+,

C-3Ј), 130.0 (+, C-2, C-4, C-6), 130.8 (+, C-2Ј), 145.51 (C_q, C-1,

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˜

q

2919, 2847, 2304, 1907, 1706, 1654, 1591, 1518, 1481, 1437, 1391,

1347, 1191, 1112, 1066, 1001, 906, 841, 818, 734, 706, 655, 627,

530, 498, 434 cm^–1. MS (FAB, 3-NBA): m/z (%) = 1210 (1) [M

+ H⁺], 1194 (2) [M + H⁺– O], 1088 (1) [M + H⁺– C₆H₄NO₂],

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Published Online: November 27, 2012

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www.eurjoc.org

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Synthesis and topological determination of hexakis-substituted 1,4-ditritylbenzene and nonakis-substituted 1,3,5-tritritylbenzene derivatives: Building blocks for higher supramolecular assemblies

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